Paper strip puller having differentially driven pullers to prevent sluing of the strip



Aug. 4 ,1910

. w. A. LLOYD 3,522,903 PAPER STRIP LER HAVING DIFFERENTIALLY DRIVEN IPULLERS PREVENT SLUING OF THE STRIP Filed March 14, 1968 2 Sheets-Sheetl mvrsmoa WILLIAMA. LLOYD FIG. I

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- a .0 Q :2 7; 41 m Q m A a 2 I j as "L N y m Q 5 ,-r' I! .1 I Q N :3 kmm 1 INVENTOR. N- l g 7 WILLIAM A. LLOYD .TIVORNEY U.S. Cl. 226-188United States Patent 3,522,903 PAPER STRIP PULLER HAVING DIFFERENTIALLYDRIVEN PULLERS TO PREVENT SLUING OF THE STRIP William A. Lloyd, SanJose, Calif., assignor to Varian Associates, Palo Alto, Calif., acorporation of California Filed Mar. 14, 1968, Ser. No. 713,003 Int. Cl.B65h 17/08 6 Claims ABSTRACT OF THE DISCLOSURE An electrographic stripchart recorder is disclosed. The recorder includes a supply roll ofelectrographic recording paper. A drive roller structure frictionallyengages the paper and pulls it from the supply roll past anelectrographic recording head which forms electric charge images to bedeveloped upon a charge retentive surface of the paper. The charge imagebearing paper is pulled past a toner station which develops the images.The drive roller includes a pair of separately rotatable drive segmentsdisposed at opposite ends of the roller and frictionally engagingopposite side edges of the recording paper. A drive motor drives theseparate drive rollers through the intermediary of a diiferential geartrain serving to divide the driving force supplied from the motor to thedrive rollers such that one of the drive rollers may rotate faster thanthe other and such that the same pulling tension force is transmitted toopposite side edges of the paper. In this manner, the paper is pulledfrom the supply roll without sluing the .paper to one side or the otherof the drive roller structure.

In one embodiment the differential gear train is contained inside of thedrive roller structure, whereas, in a second embodiment, thedifferential gear train is disposed externally of the drive rollerstructure.

DESCRIPTION OF THE PRIOR ART Heretofore, electrograhic recorders havebeen built wherein the electrographic recording paper was pulled pastthe recording head from a supply roll via the intermediary of a motordriven drive roller structure. An example of such a prior electrographicrecorder is disclosed and claimed in US. patent application 661,871filed Aug. 21, 1967 and assigned to the same assignee as the presentinvention. In this prior recorder, the drive roller extended laterallyof the strip of recording paper and frictionally engaged the recordingpaper over substantially the entire length of the outer surface of theroller.

The problem with such a prior roller structure is that if for somereason the paper starts to be pulled from the supply roll unevenly theroller will continue to exaggerate this condition causing the paper toslue across the drive roller. This can cause the recorded images on therecording paper to slue to one side or the other of the paper and whenthe paper is traveling at high rates of speed, as in excess of tens ofinches per second, it can result in wrinkling of the paper causing therecording to be improperly recorded or developed or both and can resultin a breakdown in the operation of the recorder.

3,522,903 Patented Aug. 4, 1970 ice Therefore, a need exists for animproved paper pulling structure which will cause the paper to be pulledevenly \from the supply roll to prevent a sluing of the paper as pulledfrom the supply roll.

SUMMARY OF THE PRESENT INVENTION The principal object of the presentinvention is the provision of an improved apparatus for pulling sheetmaterial from a supply roll.

One feature of the present invention is the provision, in an apparatusfor pulling sheet material from a supply roll, of a pair of rotatabledrive means engaging the sheet material on opposite sides of thelongitudinal center line of the material and including means forproportioning the drive forces applied to said pair of drive means totransmit substantially equal pulling tension forces to the strip ofsheet material on opposite sides of its center line, whereby the sheetmaterial is caused to be pulled from the supply roll without sluing sameto one side or the other.

Another feature of the present invention is the same as the precedingfeature wherein the sheet material is paper and the drive forceproportioning means includes a differential gear train having two outputdrive axles with each of said axles being connected to separate ones ofsaid pair of rotatable drive means for dividing the driving forcebetween the pair of rotatable drive means to transmit the same pullingforce to opposite sides of the paper.

Another feature of the present invention is the same as any one or moreof the preceding features wherein the pair of rotatable drive meanscomprises a pair of separately rotatable segments of a roller andwherein the outer surface of the roller is arranged to frictionallyengage the paper for pulling same from the supply roll.

Another feature of the present invention is the same as the precedingfeature wherein the roller is hollow and the differential gear train isdisposed inside the hollow roller structure.

Other features and advantages of the present invention will becomeapparent upon a perusal of the following specification taken inconnection with the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS Referring now to FIG. 1 there is shownan electrographic recorder 1 incorporating features of the presentinvention. The recorder 1 includes a pair of input terminals 2 and 3 towhich an input signal E is applied to be measured and recorded. Theinput signal is fed to a preamplifier 4 wherein it is amplified and fedto the input of an analog-to-digital converter 5. The analog-to-digitalconverter tracks the input signal E and produces a binary data output 6representative of the input signal E The binary output signal is fed toan array of electrographic writing electrodes 7 extending crosswise ofan electrographic recording paper 8 having a conductive paper backingand a thin dielectric charge retentive surface facing the array ofwriting electrodes 7.

A cylindrical frictional drive roller structure 9, more fully describedbelow, frictionally engages the paper 8 and pulls the paper 8 past thearray of writing electrodes 7 from a supply roll 11. A takeup roll 12takes up the recording paper 8 after it has passed over the drive roller9. Alternatively, the takeup roll 12 may be omitted.

The writing electrode array 7 has one of its electrodes selected andenergized by the output of the analog-todigital converter for layingdown a line charge image 13 on a charge retentive surface of therecording paper 8. The line charge image 13 is a signal tracerepresentative of the input signal E to be recorded. The signal writingelectrodes 7 cooperate with a second channel shaped writing electrodestructure 14 disposed on the conductive side of the recording paper 8and operated at a suitable potential such that the writing potentialapplied to the selected electrode of the array 7 produces approximately-400 to --900 volts relative to the channel electrode 14.

An electrographic recorder employing an array of writing electrodesenergized by the output of an analog-todigital recorder is disclosed andclaimed in copending US. application 582,767, filed Sept. 28, 1966 andassigned to the same assignee as the present invention.

An electrographic toner channel 15 is disposed facing the drive rollerstructure 9. The toner channel 15 includes a toner slot 16 cut throughthe side wall of the channel facing the roller 9 and has its marginaledges curved to conform to the curved cylindrical surface of the driveroller structure 9.

Liquid electrographic toner (ink) is supplied to the toner channel 15from a reservoir 17 by means of a liquid toner line 18. A vacuum pump 19draws a suitable vacuum on the top of the toner channel 15, as of -15inches of water, by means of a vacuum line 21. The vacuum head drawn onthe toner channel 15 causes the liquid toner within the reservoir to bedrawn via liquid line 18 into the toner channel to a predetermined levelwithin the toner channel above the toner slot 16. A float valve, notshown, controls the conductance of a vacuum bypass line to the reservoirfor maintaining the liquid level within the toner channel 15 at adesired height. A toner channel supplied with a vacuum head andinterconnected to a reservoir and including a bypass float controlliquid level means is disclosed and claimed in copending US. application577,443, filed Sept. 6, 1966 and assigned to the same assignee as thepresent invention.

A spring bias force, schematically indicated by tension spring 23interconnecting the inking channel 15 and the drive roller 9, causes thedrive roller 9 to press the recording paper 8 against the marginal edgesof the toner slot to assure formation of the liquid seal therebetween.In this manner, the vacuum head may be pulled on the toner channel 15 todraw the toner into the channel 15 and the toner slot 16. The driveroller structure 9 is rotationally driven by means of a belt 25 and apair of pulleys 26. Drive pulley 26' is driven from the shaft of a motor27, only partially shown.

An idler roller 28 is disposed on the charge retentive side of the paper8 between the recording head 7 and the supply roll 11 to assure that theelectrographic paper 8 is properly positioned with respect to thewriting array 7 and channel electrode 14. In addition, the idler rollers28 may be engraved with chart scale indices and supplied with a suitablewriting potential for laying down charge images on the recordingcorresponding to the chart scale indices to be printed thereon.

A pair of idler drive wheels 29 are carried upon an axle 31 extendinglaterally of the recording paper 8 above the drive roller structure 9. Aspring bias force, schematically 4 indicated by tension spring 32,interconnects the idler axle 31 and the axle 33 of the drive roller 9.The spring bias force between the idler rollers 29 and the frictionaldrive roller 9 causes the paper 8, at its marginal edges, to besandwiched between the idler rollers 29 and the drive roller 9, therebyassuring a good frictional engagement between the drive roller 9 and thepaper for pulling the paper from the supply roll 11.

Referring now to FIG. 2 the cylindrical drive roller structure 9 isshown in greater detail. The drive roller structure 9 includes the maindrive axle 33 extending longitudinally of and within the rollerstructure 9. The axle 33 is captured in bearings 34 at its ends topermit rotation of the drive axle 33. The drive pulley 26 is affixed tothe drive axle 33 at one end thereof externally of the drive rollerstructure 9. The drive roller cylindrical structure 9 includes a pair ofouter drive segments 35 and 36, respectively, separately driven from thedrive axle 33 via the intermediary of a differential gear train 37. Theouter drive segments 35 and 36, respectively, are formed by the outerraised portions of hollow cylindrical drive sleeves 38 and 39 which areeach supported from the axle 33 via centrally apertured headers 41holding centrally disposed axially aligned oil impregnated bushings 42such that the drive sleeves 38 and 39 are free to rotate relative to thedrive axle 33.

The difierential gear train 37 includes a pair of beveled drive gears 43fixedly secured to the transverse headers 41 at the inner ends of eachof the drive sleeves 38 and 39, respectively. A pair of diametricallyopposed beveled pinion gears 44 mesh with the drive gears 43 and arecarried at the opposite ends of a transverse axle 45 fixedly secured tothe drive axle 33. The transverse axle 45 forms a spider of thedifferential gear train 37.

The differential gear train 37 serves to divide the driving forcesupplied from the motor via the drive axle 33 between the pair ofrotatable drive segments 35 and 36, respectively. The differential geartrain 37 also permits one of the drive segments 35 or 36 to turn fasterthan the other such that the same pulling tension force is transmittedto opposite side edges of the recording paper 8. In other words, ifslack develops in the paper at one marginal edge relative to the othermarginal edge of the paper, the differential gear train 37 permits thedrive roller segment 35 or. 36 which is on the slack side to rotatefaster and to take up the slack to produce a uniform pulling tension onthe paper at opposite side marginal edges of the paper. This preventsthe paper from sluing across the roller structure 9 and assures that thepaper will be pulled uniformly from the supply roll 11.

A plurality of idler roller segments 46, perhaps better shown in FIG. 3,are disposed intermediate the outer drive segments 35 and 36,respectively. The idler segments 46 are hollow cylindrical sleevemembers having an inside diameter slightly larger than the outsidediameter of the drive sleeves 38 and 39, respectively, such that theidler segments are free to rotate independently on the drive sleeves 38and 39.

The outer surface of the drive roller 9 is formed by a relatively thinlayer 47, as of 0.063" thick, of a compressible resilient materialhaving relatively high frictional characteristics for frictionallygripping the paper 8. The outer surface layer 47 should also bechemically inert to the liquid toner. Such a resilient material includesthe synthetic elastomers such as polyurethane and neoprene. Thecompressible resilient characteristic of the outer layer 47 of the driveroller structure 9 facilitates formation of the liquid seal between thepaper 8 and the marginal edges of the toner slot 16 and, in addition,permits the drive roller 9 to frictionally engage the surface of theidler rollers 29 at the outer marginal edge of the paper 8 such that theidler rollers 29 can be frictionally driven from the drive rollerstructure 9, thereby producing a double frictional drive action on thepaper 8 which is sandwiched between the drive roller structure 9 and theidler rollers 29.

In a typical example of a drive roller structure 9, such a structure hasbeen employed to pull a wide strip of electrographic paper which isapproximately 0.0035" thick at a speed of approximately 150" per secondwithout encountering sluing and wrinkling of the paper 8.

Referring now to FIG. 3 there is shown an alternative paper drive rollerstructure of the present invention. Drive roller structure 9' of FIG. 3is similar to that of FIG. 2 except that the differential gear train isdisposed externally of the drive roller structure 9'. The drive rollerstructure 9 of FIG. 3 is especially suited for applications where thedrive roller is too small in diameter to house the differential geartrain structure 37. In the drive roller structure 9' of FIG. 3, thedrive roller segments and 36 together with-the idler roller segments 46are separately rotatably supported upon an axle 33. A pair of drivepulleys 48 and 49 are fixedly secured to the separate drive rollers 35and 36, respectively. Drive belts 411 and 52 interconnect the drivepulleys 48 and 49, respectively, with drive pulleys 53 and 54,respectively, which latter pulleys are fixedly secured to outputs driveaxles 55 and 56 of the diiferential gear train structure 37. Output axle55 comprises a sleeve rotatably and con centrically supported withrespect to a centrally disposed drive axle 57 which is driven from themotor 27 via pulleys 58 and a drive belt 59. The spider 45 of thedifferential gear train 37 is fixedly secured to the end of the driveaxle 57. Drive axle 57 and output drive axle 56 are rotatably supportedat their ends in bearing assemblies 61.

In operation, the roller drive structure 9' of FIG. 3 operates insubstantially the same manner as previously described with regard toFIG. 2 to produce a uniform pulling tension on the paper at oppositemarginal side edges of the paper.

Although the differentially driven paper pulling drive roller structures9 and 9' of FIGS. 2 and 3 have been described as employed in anelectrographic recorder, this is not a requirement. The paper pullingapparatus of the'present invention may be utilized to advantage whereinit is desired to pull continuous strips of sheet material from a supplyroll without encountering sluing of the sheet material as drawn from thesupply roll. More particularly, the sheet material need not be paper butmay include other types of sheet material such as thin sheets ofplastic. In addition, the drive roller structure '9 need not be limitedto a frictional engagement with the paper ,or sheet material but mayinclude sprocket type drive wheels wherein the teeth of the sprocketengage a series of perforations distributed along the marginal sideedges of the sheet material being drawn from the supply roll.Furthermore, the paper pulling apparatus of the present invention neednot be limited in its use with electrographic recorders but may be usedwith other recorders and printers such as, for example, in electrostaticcharacter printers and electrophotographic imaging devices.

Since many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a transport apparatus for pulling a continuous strip of sheetmaterial comprising:

a pair of rotatable drive means for transmitting two pulling tensionforces to the strip of sheet material on opposite sides of thelongitudinal center line of the strip of sheet material;

means for applying a drive force;

a differential train gear means powered by the means for applying adrive force and having a pair of drive axles one of which is connectedto each of the rotatable drive means for permitting one of the rotatabledrive means to rotate faster than the other and for proportioning thedrive force to transmit substantially equal pulling tension forces tothe strip of sheet material on opposite sides of the longitudinal centerline to prevent sluing of the sheet material;

the improvement which comprises a roller device for engaging and pullingthe strip of sheet material, and the pair of rotatable drive meanscomprising a pair of separately rotatable segments of the roller device.

2. The apparatus of claim 1 wherein the roller device is hollow and thepair of rotating drive means and the differential gear train means aredisposed therein.

3. The apparatus of claim 1 wherein the outer surface of the rollerdevice frictionally engages the strip of sheet material for pulling thesheet material.

4. The apparatus of claim 1 wherein at least one idler segment isprovided on the roller 'device which is freely rotatable relaitve to theseparately rotatable segments.

5. The apparatus of claim 4 wherein the separately rotatable segments ofthe roller device are disposed at the opposite ends of the roller deviceand further wherein at least one idler segment is disposed between theseparately rotatable segments.

6. The apparatus of claim 1 including a pair of idler wheels, means forspring biasing the idler wheels toward the separately rotatable segmentsfor sandwiching the sheet material between the separately rotatablesegments and the idler wheels to increase the frictional engagementbetween the separately rotatable segments and the sheet material.

References Cited UNITED STATES PATENTS 3,052,396 9/1962 Butscher 226l923,119,537 1/1964 Smits 226-188 X RICHARD A. SCHACHER, Primary ExaminerUS. Cl. X.R. 226-190,

